Seeking advice on stove for small sauna.

I have a lifetime of experience with wood stoves...but, know nearly nothing about rocket stoves other than what I have seen on the Net and read in Ianto's book.

I plan to build a small sauna...roughly 6' x 6' with a low head height. My initial thought was to make a simple rocket stove out of a 5 gallon metal can, and line the outside with rocks...or place them on top. I fear that the metal will burn through too quickly though...and, by the time I lined its outside with rocks, it might take up more space than I want. That size may be too much (too hot) for my sauna size too, I don't know.

My most recent thought is to build a rocket stove from rock...but I have no idea where to start...and, for now, I'd rather not have to experiment with a bunch of designs. That said, it would be nice if it were simple and easy to build. I have experience doing mason work and cob....have a welder too if making something from metal.

Can someone give me some direction like links and/or articles...and advise on rocks to use as well? I have lava rock that I've used successfully in a temporary sauna...and lots of basalt.

I built a rocket stove of sorts to heat our sauna. if I knew then what I know now, I would do some things differently. if I get my act together, I may do a rebuild this summer.

one important thing to remember is that the standard rocket mass heater is designed to provide long-term, gentle heat. that isn't really ideal for a sauna, where short-term intense heat is generally desired.

so probably less mass is in order, as well as a bell that will exchange more heat than the standard design.

Rusty :
just one vote for a 'pocket rocket ', Which is the much simpler ancestor of the rocket stove mass heater and will work with a much smaller diameter stove pipe than the R.S.M.H. ! A look at Ianto Evans' book " rocket mass heaters " pg 76,77-ish should give you all you want for info ! - check out the similar threads section just below this thread to get a link to others thoughts !

We all learn by doing/sharing, so don't be afraid to come back here and post your results ! Pyro magicly, Big Al

Sandy Mathieu wrote:This was my thought on the topic, only the water would cover the barrel top.

that could work, but it would be a very steamy sauna. I personally like to be able to regulate the humidity by throwing water on the kiuas. that way, it can get nice and hot with low humidity, and then toss some water on for good löyly.

allen lumley wrote:Rusty :
just one vote for a 'pocket rocket ', Which is the much simpler ancestor of the Rocket Stove Mass Heater and will work with a much smaller diameter stove pipe than the R.S.M.H. ! A look at Ianto Evans' book " Rocket Mass Heaters " pg 76,77-ish should give you all you want for info ! - Big Al

Thanks! That was my first thought...but I'm concerned that the thin metal would burn through too quickly. How many fires can these metal cans take, roughly?

Rusty B. : Fast answer, I don't know, It will depend on how often you use it and how often you remove the ashes which contain Lye. It will also depend on
how hot you run the stove. If you can restrain your self and NOT over feed the stove to the point that the bottom 1/3rd of your barrel glows red hot, then
conservatively 100 - 150 burns with a decent barrel. This is NOT from personal experience burning a Pocket rocket to failure, this is from using a barrel stove
that never seemed to get cleaned out, and 1/2-ing the results! There are several hi-temp paints for the outside of the barrel but, the only protection for the
inside of the barrel is sensible burning and careful cleaning ! I expect that the inverted feed tube that goes down into the barrel will fail first with this piece of
stove pipe needing replacement 2-3 times (or more, If you use lightweight or used stovepipe) before the barrel needs to be replaced ,so you will have lots
of warning !

I need to raise two more points, You will need to burn out / burn off the barrel outdoors carefully to include sanding off the outside of the barrel after your
controlled burn, What I recommend doing is waiting until you can find a metal 5 gal pail to prepare as clearly mentioned in the ''rocket mass heaters'' book.
Make and fire your 1st Pocket Rocket out doors and learn how to feed it sensibly, and you will have a great little heater that can take the chill of working
outside these cold spring mornings, or let this one get red hot and use it to melt deep ice off of your sidewalks, and driveways, Much of the heat radiates
off of the sides of the barrel way down at the very bottom - warm toes ! Warning you can set your blacktop on fire ! This will give you a feel for this type of
stove, and operating it safely ! I would use as few elbows as possible !

We used this as a project for Webilo Scouts, for Ice Fishing outings, and had an Uncle take one back to Michigans Upper Peninsula, where they were buying
the 5 gallons of driveway sealer, saving the sealer and making their Pocket rocket that way !

If this interests you, let us know how this project works for you ! For the good of the Craft, be safe, keep warm, PYROmagically - Big AL

I've been building and using rocket stoves for about 10 years now, taught directly by Ianto at a couple of his classes in Cob Cottage (you should go if you can... amazing). I have a 15-gallon "pocket rocket" that heats an upstairs room that has been cleaned only once in 5 years. I cook it hard since it has a cob wrapper on about 3/4 of it's surface. The interior is fine. The barrel has no bottom, instead it sits on two fire bricks, which site on cob which sits on "insulation cob". I have a metal cutout that sits on top of the two fire bricks as the bottom, which can be replaced (but hasn't been yet).

The feed tube gets replaced about once a year because it takes a beating. My exhaust pipe is still going strong - no signs of wear-through yet. The previous poster gave critical advice. Burn the hell out of your bucket before you take it indoors. I make a fire on my side walk and roast the inside and outside of the barrel which removes everything and also imparts a nice metallic black finish. Cook the lid too.

I am building a sauna now and plan to use a 5-gallon pocket rocket with 6-inch feed tube and 3-inch exhaust pipe. That about takes up the available space on your lid. I'll put the stove on top of a pad of insulate cob with dry rocks stacked up around it. If the rocks seem too bulky, trust me, you will want them. Your bucket will glow and you want the rocks to absorb the radiated heat or it will fry the wall.

I have two rocket stoves inside my house, which is a conventional stick frame house. I install 2x2" wood over my sheetrock on top of studs. Place tile-backing fiber board over that to cover the entire space along the wall that will touch the cob. Fill the spaces with perlite from the open edge at the top then cap it off with another 2x2" board running horizontal (to the finish height of your bench/stove). This will keep your house from burning down. But you need more than that for the stove area. Use insulation cob made with clay slip and sawdust or whatever. See Ianto's book for ideas. I have a shop and lots of sawdust so that is my preference.

More hints: after getting my thumb sewn up, I always fold back the rim of the feed tube about a quarter inch to make a nice smooth edge. Cut ducting pipe is super sharp and you reaching down there a lot. I tried aluminum tape once but it just burns off the sticky and then falls off. Burn the bucket and lid in an open fire outside until it's a gorgeous metallic black. Your lungs will love you.